The present invention relates generally to pumps, and, more particularly, to innovations and improvements which provide an ink pump system that maintains a substantially uniform ink viscosity and utilizes a gear pump without seals which is submerged within the ink reservoir and is self-lubricated by the ink of the system.
In ink pump systems, it is desirable to maintain the ink used in the system and contained in the ink reservoir at a substantially uniform viscosity. This can be accomplished by monitoring the viscosity of the ink contained in the ink reservoir and adding thinner or solvent from a solvent reservoir to the ink as necessary to maintain the ink's viscosity at a predetermined substantially constant value.
In a known prior ink pump system, a gear pump for pumping and circulating the ink to the desired location for a printing application was located externally from the ink reservoir. The external gear pumps of the prior art system have been subject to one recognized problem in that the seals of these external pumps begin to leak after a relatively short period of operation. This leakage is apparently due to the deleterious effect of the solvent in the ink on the pump seals.
The ink pump system of the present invention overcomes the aforementioned problem by utilizing a new design of a gear pump designed to be submerged in the ink reservoir. The seals of the gear pump are omitted and the pump is specifically designed so that the ink is used as a lubricant for the rotation of the gear shafts. The pump further utilizes a layer of ink to suspend the gears between the top and bottom surfaces of the pump chamber in order to reduce wear.